Method of fabricating a heat exchanger from corrugated sheets



Dec.. 8,1970 D. M.Qx 1 3,545,062

METHOD OF FABRICATINQA HBA-T EXCHAXGER FROM C RRUGATED SHEETS Original Filed July 19. 1967 l -2 Sheets-Sheet 1 n /h/k/ De 8, 1970 n. M. cox.

METHOD OF- FABRICATING A HEAT EXCHANGER FROM CORRUGATED SHEETS 2 Sheets-Sheet 3 Original Filed July 19, 1967 ATTORNEY United States Patent O 3,545,062 METHOD OF FABRICATING A HEAT EXCHANGER FROM CORRUGATED SHEETS Dean M. Cox, Whitestown, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application July 19, 1967, Ser. No. 654,606, now Patent No. 3,451,474, dated June 24, 1969. Divided and this application Oct. 2.8, 1968, Ser. No. 770,921

Int. Cl. B21d 53/02 U.S. Cl. 29-157.3 3 Claims ABSTRACT OF THE DISCLOSURE A heat exchanger and a method of making it. Corrugated sheets are folded into wafers, sealed, stacked, brazed together at the ends, and the braze metal and ends of the folded sheets cut away to open passages through the wafers from end to end. The stack is enclosed in a pressure-containing case which confines a fluid which flows between the wafers.

This application is a division of my application Ser. No. 654,606, for Heat Exchanger, filed July 19, 1967, now Pat. No. 3,451,474.

My invention is directed to a method of making improved heat exchangers of the fixed or recuperator type. While my invention is capable of various uses, it is particularly suited to provision of a recuperator for use in gas turbines and other systems in which a large heat transfer area is required to transfer heat from a gas at relatively low pressure to another gas at relatively high pressure.

My invention provides for the manufacture of a heat exchanger in which there are no high pressure passages in the ordinary sense, the high pressure path extending between a number of wafers each defining a low pressure path through the heat exchanger, the high pressure gas being confined by a casing which encloses the heat exchange pack made up by the wafers.

The principal objects of my invention are to provide a compact and leak-free heat exchanger particularly adapted for use with gases at substantially different pressures, to provide a heat exchanger of small weight and volume for its heat transfer capacity, to provide an inexpensive and feasible mode of manufacturing heat exchangers, and, more specifically, to provide a heat exchanger in which the structures defining the low pressure passages are wafer-like in configuration and are formed of corrugated sheets such that the corrugations engage to preserve the separation of the sheets of the wafer and also to define passages between the wafers for the other fluid.

The nature of the invention will be more clearly apparent from the succeeding detailed description of a heat exchanger and of the preferred embodiment of a process for manufacturing such a heat exchanger.

FIG. 1 is an axonometric View, with parts cut away, of a heat exchanger of a cross-counterliow type.

FIG. 1A is a fragmentary sectional view taken on its plane indicated by the line 1A-1A in FIG. l.

FIG. 2 is a partial cross section of the same on a plane indicated by the line 2-2 in FIG. l.

FIG. 3 is a view of a corrugated sheet.

FIG. 4 is a view of the same after folding and seam welding to form a wafer.

FIG. 5 is an axonometric view of a stack or pack of wafers.

FIG. 6 is a partial view of the same after brazng the end of the pack.

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FIG. 7 is a fragmentary cross-sectional View of the same to an enlarged scale as indicated by the line 7-7 in FIG. 6.

FIG. 8 is a view similar to FIG. 7 after opening the ends of the wafers.

FIG. 9 is a partial end view of the pack as indicated by the line 9-9 in FIG. 8.

FIG. 10 is a fragmentary sectional View of the same taken on the plane indicated by the line 10-10 in FIG. 9.

Referring first to FIGS. 1, 2 and 3, the heat exchanger comprises a pressure containing casing 13 in the general form of a rectangular tube 14 having end fianges 16 fixed to the ends of the tube. The tube includes an inlet side wall 17 having an inlet at 18 for high pressure gas and an outlet side wall 19 opposite to side 17 defining a high pressure gas outlet 20, and includes two intermediate walls 22. One end fiange 16 defines a rectangular inlet 23 and the other defines a similar outlet at the other end of the casing. Each end fiange is of L section including a radially extending portion and an axially extending portion 25 which fits within the fiared end 26 of the tubular casing section 14. These parts are brazed or otherwise bonded and sealed together.

The interior of the casing is filled by a heat exchange pack 30. This heat exchange pack is made up of a stack of wafers 31, each wafer being a folded corrugated sheet to be described, having parallel walls 32. The walls of the wafers are parallel to the casing sides 22 and thus the wafers present their ends to the end flanges 16 and their edges to the sides 17 and 19 of the casing. The wafers have walls with corrugations as indicated at 34 in FIGS. 1, 3 and 4 which extend generally from end t0 end of the wafer but are, preferably, inclined about 10 degrees to the endwise direction of the wafer. The corrugations on opposite walls of a particular wafer are inclined oppositely to the axial direction so that the corrugations cross and engage each other where they cross. Each wafer has a folded edge 35 and a sealed (preferably seam welded) edge 36.

As will be more clearly apparent from FIGS. 3 and 4 each wafer preferably is made from a rectangular sheet 38 having ends 39 and sides 40 and which is provided with corrugations over substantially the entire surface, the corrugations extending at about a ten degree angle to the sides 40. Preferably the margin of the sheet adjacent the sides and ends and a strip 41 through the center between the sides of the sheet are not corrugated.

The sheet is made into a wafer by folding the sheet along the central uncorrugated line 41 so that the two sides 40 meet as shown in FIG. 4. After the folding, the two edges 40 are seam welded together and the ends 39 are closed by seam welding so that the wafer becomes temporarily a sealed capsule. When the sheet is folded, the corrugations on the opposite walls of the wafer are inclined to each other by about twenty degrees. Thus, they cross over at numerous points to abut each other and hold the walls of the wafer apart. Also, when the wafers are stacked to form a pack 42 as illustrated in FIG. 5, the corrugations of adjacent wafers cross so that the peaks of the corrugations contact each other. The wafers 31 are stacked to provide a sufficient size heat exchange pack 42 to fill the rectangular casing 13.

The seamed ends of the pack are then filled with braze metal at each end as indicated at 43 in FIGS. 6 and 7. This Imaterial covers the ends 39 of the wafers and also fills the space between the wafers to the plane -44 indicated in FIG. 7 to hold the wafers together. The braze metal does not enter the wafers because these are closed at the fold and at the seam-welded side and ends.

The next step in making the heat exchange pack is to machine away the ends of the pack as shown in FIGS. 8 and 9 to a plane face 4S back of the end seam so that the ends of the wafers are opened. However, the machining does not remove the braze metal remaining at 46 between the ends of adjacent wafers. This braze metal not only holds the matrix pack assembledbut it also blocks the ends of the passages between adjacent wafers as indicated at 46 in the FIGS. 8 to 10.

The structure of the heat exchange pack should be clear from the foregoing description of the assembly and of the process of manufacture. The lower pressure gas can ow into the wafers through openings 48 at one end of the pack 30 and out the similar openings at the other end. The high pressure gas can come into the entrance 18 and flow out the entrance 20, flowing both across and lengthwise of the matrix pack between adjacent wafers 31. The high pressure gas is confined by the casing 13.

The end anges 16 of the casing are brazed or otherv wise sealingly assembled to the matrix pack either at the same time that the braze metal 43 is applied, or later. The outer casing 13 may be wrapped around the flanges 25 and welded or brazed to the flanges to complete the fluid-tight casing. Alternatively, the flanges 16 may be initially provided on the casing portion 14 and the heat exchange pack thereafter slipped into the casing and sealed at the ends to the wall of the casing by any appropriate means to prevent leakage of the higher pressure gas around the exterior of the heat exchange pack at the ends of the heat exchanger.

D'ucts to conduct the hot and cold gases to and from the heat exchanger, may be of any suitable configuration and attached by any suitable conventional means (not illustrated). As will be apparent, the relatively inclined corrugation of the heat exchange wafers provide a means whereby each wall has an array of points at which it abuts the adjacent wall and also provides a very substantial gas passage between it and the adjacent wall, whether this be a hot gas or a cold gas passage. Also, the relatively inclined corrugations promote turbulence and good heat conduction from the gas to the thin sheet metal wall, or vice versa. Because of the type of structure described, the walls between the hot low pressure gas and the cold high pressure gas may be quite thin, thus promoting compactness, light weight, and efliciency of the heat exchanger.

It may be noted that the drawings are not intended to show the structure to scale since the walls may be very thin as a practical matter. In a particular embodiment it is The process described above provides for a very easy and economical manufacture of such a heat exchanger pack.

Obviously, the wafer can be made from two sheets each corresponding to half of sheet 38, the wafers beingseam welded together around the entire margin.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modications may be made by the exercise of skill in the art within the scope of the invention.

I claim:

1. A method of making a heat exchange structure cornprising, in combination, the steps of: corrugating a plurality of sheets, sealing the ends and the sides of pairs of corrugated sheets to provide a plural number of sealed waferelike capsules, the corrugations of the walls of each capsule being so disposed that the corrugations cross at a two-dimensional array of points, stacking the capsules in mutual alignment, the corrugations of adjacent capsules being so disposed that the corrugations cross at a two-dimensional array of points when the capsules are stacked, filling the spaces between adjacent capsules with a solid binder to a predetermined distance from each end of the capsules, and cutting away the ends of the capsules and the binder to a distance sucient to open the sealed ends but less than the said predetermined distance to provide a References Cited UNITED STATES PATENTS 3,115,447 12/ 1963 Stengel. 3,183,963 5/1965 Mondt 165-166X 3,274,672 9/1966 Dore 29-157.3 3,341,925 9/1967 Gerstung 113-118X FOREIGN PATENTS 588,426 12/ 1959 Canada. 896,171 5/ 1962 Great Britain.

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner U.S. Cl. X.R. 

